Electric circuit breaker



Dec. 3, 1940. o. c. TRAVER ELECTRIC CIRCUIT BREAKER w/////// n////// .aI. a.

Ifiventor": Olive? C. Tr ver: y I'lis ttorrwey.

Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE ELECTRIC CIRCUITBREAKER Oliver 0. Traver, Drexel Hill, Pa, assignor to genital ElectricCompany, a corporation of New Application September 1, 1 939, Serial No.293,085 6 Claims. (01. 200-149) The present invention relates toelectric cirstationary contact I are pressed when the switch cuitbreakers, and more particularly to expulsion is assembled. type circuitbreakers in which the arc is extin- The movable contact of the switch isin the guished by gas liberated from the walls of an arcform of anelongated hollow rod l1 having an exconfining chamber under the actionof the arc tension or pencil it of insulating material secured heat. tothe inner end thereof in any suitable manner In breakers of the gasexpulsion type the as by the screw-threaded connection illustrated.amount of gas available for extinguishing the The movable contact I! isarranged to engage the arc is dependent upon the arc heat and, as arefixed contact H in the closed circuit position of i0 suit, the amountof gas available when the curthe circuit breaker to complete a circuitfrom m rent being interrupted is small is sometimes inthe conductinghousing which may serve as one sufllcient to successfully interrupt thearc. If terminal of the breaker to the other terminal of the arcpassageismade of sufllciently limited area the breaker y a SuitableSleeve Co t ct ot to create an effective arc-extinguishing gaspresshown). The movable contact is reciprocated in sure by the smallamount of gas liberated when a the -c fi tube y y Suitable e 1 lightcurrent are is drawn, destructive pressures anism (not shown) in amanner well understood will be built up in the restricted arc-confiningby those skilled in the art. passage when a heavy current are is drawn.This As the movable contact [1 is withdrawn from characteristic ofbreakers of this type oft n prethe fixed contact during thecircuit-interruptvents their use where a wide range of currents ingOperation of the breaker, the pencil I8 is 20 must be interrupted. It isaccordingly an imdrawn into the passage in the arc-confining tubeportant object of the inventi n t provide n imlli defined by the liner[3. In accordance with proved construction and arrangement in circuitthe present invention the movable contact and breakers of the above typewhich is effective to the filler pencil l8 are made as nearly the size 5interrupt currents of widely varying magnitude. of the passage throughthe liner l3 as possible Further objects and advantages of the presentwithout causing undesirable friction between the invention will becomeapparent as the following relatively movable parts, so that there isvery description proceeds, reference being had to the little spacebetween the inner wall of the liner accompanying drawing in which Fig. 1is an elei3 and the outer surface of the movable contact.

vational view in section of a circuit breaker em- In order to providearc-confining passages, the 30 bodying the invention; Fig. 2 is asectional view filler Pencil s provided with a plurality o taken alongthe line 2-2 of Fig. 1, and Fig. 3 grooves l9 which extend generally inthe direcis an elevational view of a modification thereof. tion of therelative movement between the fixed Referring to Fig. 1, I have shown myinvention and movable contacts. The grooves l9 are conembodied in acircuit breaker comprising an arcnec ed o e y a Passage 20 o ed on the35 confining structure ill in the form of an elongated surface of thepencil l8 and extending sufiiciently tube of insulating material. Thetube In is conaround the same to form a headerjor the grooves nected toa supporting insulator H by a two-part S. The passage 20 is preferab yformed adhouslng ll of conducting material. The tube l0 jacent the innerend of the movable contact ll is provided with a lining of gas-emittingmatewhere it is in communication with a root of the 40 I rial which, inthe present case, is in the form of arc and will be effective todistribute the current a removable liner l3 which is recessed at itsupof a heavy C e t arc O g the o es H in per end to receive a fixedcontact I. The liner a manner which will be more fully set out at a issecured in the tube III by a threaded member later point in thespecification.

Ha which engages the lower end of the tube. In some applications it isdesirable to provide 45 The contact II is annular in shape and formed anarc passage of increasing cross-sectional area of a plurality ofspring-biased segments. The as the contacts are separated, in order toprocontact is connected to the housing I2 in any vide a larger space forthe heated gases and to suitable manner as by the conducting strips I5preven o rea an i cr in pr ur This 'which are clamped between the upperpart of desirable feature may be incorporated readily in 50 the housingand an annular washer l6 of insuthe present construction by simplyincreasing lating material. The washer is received between thecross-section of the grooves I! as they ap the two parts of the housingat its outer edge and proach the end of the pencil. This is a simpleextends inwardly to form a header against which operation from amanufacturing standpoint and the arc-confining tube ll, the liner l3 andthe permits the construction of a switch having an 55 arc-confiningpassage of progressively varying cross-section without appreciablyincreasing the expense of manufacture. -In other applications it may bedesirable to decrease the cross-sectional 5 area of the arc-confiningpassage as the separation of the relatively movable contacts increasesin order to provide a snufling action on the arc. For such installationsthe grooves I 9 may be formed with gradually decreasing cross-section 0as the distance from the movable contact increases. Such a constructionis particularly adapted for use in breakers handling relatively smallcurrents where the quantity of arc-extinguishing gas liberated is smalland the snufllng action of the tapered arc-confining passage aids inincreasing the pressure of the gas available for extinguishing the arc.

In the arrangement shown the arc-confining tube l0 and the liner I3 areprovided with intermediate passages 2| which communicate with theinterior of an expansion chamber 22 secured to the exterior of thearc-confining tube 10 in any suitable manner as by the screw-threadedconnection illustrated in the drawing. The ex- 'pansion chamber whichpermits the highly heated and ionized gases exhausted from thearc-confining chamber to expand and cool before they are exhausted intothe surrounding atmosphere is, as illustrated in the drawing, dividedinto upper and lower expansion chambers 23 and 24 by a transverselyextending partition 25 having openings 26 formed therein. Suitablemufliers 21 in the form of wire mesh are provided in each of theexpansion chambers to deaden the sound of the arc and to aid in coolingand removing the metal vapor or particles from the hot gases before theyare exhausted to the atmosphere through openings 28 formed in the outerwall of the chamber 22. The advantages of the structure described abovewill be better understood from a consideration of thecircuit-interrupting operation of a breaker in which it is embodied.With the contacts of the breaker in their closed circuit position, asillustrated, a circuit is completed from the housing l2, through thestrip I5, the fixed contact 14, the movable contact II, to the otherterminal of the breaker (not shown). When the movable contact is moveddownwardly to separate it from the contact I the pencil I8 is drawn intothe interior of the arc-confining tube l0 and an arc is drawn betweenthe relatively movable contacts. As previously pointed out, the interiorof the lining of the arc-confining tube conforms closely in size withthe outer surface of the movable contact I! and the filler pencil l8attached thereto so that the arc, when drawn, is confined within one ofthe grooves N. If the current is small, the gas liberated from the walls50 of the groove and the liner I3 is small and the resulting pressure,while not great, is suflicient to extinguish the arc confined in thesingle groove. As the contact I! is withdrawn from the arc-confiningtube the gases liberated by the 5 are are exhausted through the passages2| into the expansion chambers 23 and 24 and into the atmosphere throughthe passages 28. When the movable contact is'completely withdrawn fromthe arc-confining tube the gases may also exhaust directly from thelower end of the tube.

If a large current is being interrupted the arc drawn in one of thepassages l9 liberates larger amounts of arc-extinguishing gas because ofthe greater are heat. The provision of the passage 20 for connecting thegrooves I 9 together provides means for transferring the gases from onegroove to the other and for dividing the are into a plurality ofparallel branches. Placing the passage 20 adjacent the end of themovable contact at which the arc is drawn renders it very eifective tocause a division of the are when the current is large. The splitting ofthe heavy current arcs by the structure described above may beunderstood from a consideration of the voltage current characteristicsof a closely confined electric arc. When an arc is unconfined the arcvoltage decreases with an increase in current and, under suchcircumstances, a division of the arc would not occur. However, when anarc is closely confined, as with the present construction, the voltagedrop across the arc increases with the current flow after a certaincurrent level is reached and, under these circumstances, the arc willseek a parallel path and .a divided arc will be maintained whenever itcan be established with a lesser voltage gradient than that required tomaintain the total arc current in a single groove.

Thus, it is seen that the present construction provides a circuitbreaker having a plurality of arc-confining passages electrically inparallel and adapted to be brought into use automatically by theconditions created in the arc-confining structure by the arc itself. Asa result, the conditions existing in any one of the arc-confininggrooves l9 vary over a relatively small range as compared with the rangeof currents being interrupted since any increase in current value beyonda certain point will cause a division of the are among two or more ofthe grooves. This action results in more uniform interruptingcharacteristics and, at the same time, increases the range of currentswhich may be interrupted by the breaker.

In Fig. 3 I have shown a filler pencil 30 which may be substituted forthe pencil l8 shown in Fig. 1. In accordance with the modificationillustrated in this figure a plurality of spiral grooves 3| are providedin the surface of the pencil 30 and are connected together at theirlower ends by a connecting passage 32. The use 1. An electric circuitbreaker of the expulsion type comprising means defining an arc passage,a fixed contact, a movable contact engaging said fixed contact in theclosed circuit position of said breaker and separable therefrom to drawan arc in said passage and a member of insulating material movable intosaid passage upon circuit-interrupting operation of said breaker, thewalls of said arc-confining passage and said insulating member beingclosely fitting and gas emitting under the action of the arc and shapedto provide a plurality of interconnected grooves extending generally inthe direction of separating movement of said contacts and providing aplurality of arcconfining passages.

2. An electric circuit breaker comprising means defining an elongatedpassage, a stationary contact, a movable contact extending into saidpassage and engaging said fixed contact in the closed circuit positionof said breaker, a member of insulating material connected to saidmovable contact and movable therewith into said passage when saidmovable contact is moved toward circuit-interrupting position, thecooperating surfaces of said member and the walls of said passage havinga plurality of interconnected grooves formed thereon to provide aplurality of arcconfining passages.

3. An electric circuit breaker of the gas expulsion type, comprisingmeans defining an elongated arc-confining chamber, a fixed contact, amovable contact movable in and closely fitting said arc-confiningpassage, an extension of gasemitting material on said movable contactarranged to be drawn into said arc-confining passage upon separatingmovement of said fixed and movable contacts, said extension beingprovided with a plurality of grooves extending generally in thedirection of separating movement of said contacts and a passagecommunicating with said grooves adjacent the end of said movable contactand providing for the free transfer of arc gases from one groove toanother and a division 01' the arc among the grooves in accordance withthe magnitude of the arc current.

4. An electric circuit breaker of the expulsion type comprising meansdefining an elongated passage, a stationary contact, a movable contactextending into said passage and engaging said fixed contact in theclosed circuit position of said breaker, a member of insulating materialconnected to said movable contact and movable therewith into saidpassage when said movable contact is moved toward circuit-interruptingposition, the cooperating surfaces of said member and the walls of saidpassage having a plurality of interconnected spiral grooves formedthereon to provide a plurality of arc-confining passages.

5. An electric circuit breaker of the expulsion type, comprising meansdefining an elongated arc-confining chamber, a fixed contact, a movablecontact movable in and closely fitting the walls said arc-confiningchamber, an extension of insulating material on said movable contactarranged to be drawn into said arc-confining chamber upon separatingmovement of said fixed and movable contacts, said extension beingprovided with a plurality of spiral grooves extending generally in thedirection of separating movement of said contacts and a passagecommunicating with said grooves adjacent the end of said movable contactand providing for the free transfer of gas from one groove to another.

6. An electric circuit breaker of the gas expulsion type comprisingmeans defining an elongated passage, a stationary contact, a movablecontact extending into said passage and engaging said fixed contact inthe closed circuit position of said breaker, a member of insulatingmaterial connected to said movable contact and movable therewith intosaid passage when said movable contact is moved towardcircuit-interrupting position, the cooperating surfaces of said memberand the walls 01' said passage being shaped to provide a plurality ofinterconnected arc-confining passages having a cross-sectional areavarying progressively with the separation of said fixed and movablecontacts.

OLIVER C. TRAVER.

